Dig a hole 3 squares deep, 2 squares wide.
Stand in the middle of the hole so you're touching both squares of the floor of the hole you made.
Use a gravity-affected block (I.E. sand or gravel) and drop two blocks above you.
Walk slightly into the stacked up sand/gravel that you SHOULD be standing half way in and look around. You will get a view of all the cave systems within the viewing distance that you have set in your map.